Once you've taken down the Siren you can leave the cemetery.
Lutece instructs you to follow the phantom trail to the three tears (which results in two more fights with the Siren).
Fight a Crow, a Fireman, and their underlings to enter without trouble. The Code Book you found in Downtown Emporia will come into play near the bank vault.
After battling through the main room of the bank, the footsteps lead to the right. Instead, head left where you'll find the room that corresponds to the code book after going down a hallway.
Use of the storm hat is highly recommended as you can easily chain the effect through a group using very few salts.
After you have cleared all her support away the fight becomes very easy on any difficulty level.
You can also lock-release Flash by pressing on the "puzzle" icon in the top right corner of your browser.
The Repeater, Carbine, or Sniper Rifle are good weapons to use on the creature (from a distance), but keep the reliable Shotgun handy (and full) for closer encounters.
Note that regardless of who you target, the Siren will keep reviving enemies as part of its attack pattern. Hide in the alcove with the medkits and use the large coffin for cover. A good tactic to use is to get rid of her support first then attack her.
To do this you must use the Shock Jockey or Devils Kiss vigors as any enemy killed while under the effect of one of them will disintegrate upon death and cannot be .
It can be a bit tricky to get the torches to ignite, since the fireballs like to bounce off before exploding, but with a few tries you should get it.
This section is an homage to a similar puzzle in the original Bioshock.